I have always been envious of people who can get by with only six hours' sleep. I prefer eight, sometimes more. I can function on six, but after a few days my brain will be way below full capacity.
How much sleep we get affects us all. Too much sleep makes us groggy and disorientated. Sleep too little and our mood and concentration suffer. If this carries on it can also cause serious health issues, heightening the risk of diabetes, obesity and high blood pressure.
Most of us sleep between six to nine hours a night, meaning we spend about a third of our lives asleep. This may seem like a long time, but we actually sleep the least among all the primates - the group that includes monkeys, apes and us.
So says a new analysis looking at the impact sleep has had on our evolution. The new research suggests that humans have evolved to sleep less, but also to sleep very deeply. This may help explain our success as a species.
Three million years ago, our ancestors still had ape-like bodies. These Australopithecines probably slept in the trees, like modern chimpanzees.
But by two million years ago, hominins had become fully upright. Homo erectus spent its life on the ground, and may have been the first hominin to make beds there. If that is true, we have been sleeping on the ground for a long time.
Sleeping on the ground may have gifted H. erectus with a higher-quality, more restful sleep.
For one thing, they did not have to worry about falling out of the trees. What's more, while the risk from predators was higher on the ground, they had ways to protect themselves.
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